Studying Solar Wind Magnetic Reconnection Events using the Cluster 4-point

Measurement Capability

A.C. Foster1, C.J. Owen1, A.N. Fazakerley1, C. Forsyth1 E. Lucek2, H. Rème3

1. UCL, Mullard Space Science Laboratory, Surrey, UK2. Imperial College, London, UK3. CNRS, IRAP, Toulouse, France

UCL DEPARTMENT OF SPACE & CLIMATE PHYSICSMULLARD SPACE SCIENCE LABORATORY

Magnetic Reconnection Observables

•First study of solar wind reconnection made by Gosling, 2005.•Bifurcated current sheet•Magnetic field rotations over current sheets•Enhanced plasma jet / reconnection exhaust

Reconnection Exhaust

Reconnection Exhaust

Adapted from Gosling, J.T. (2005)

Inflow

Inflow

Inflow

Inflow

Magnetic Field LinesCurrent Sheet

A1 A2

B

B

Phan,T.D (2006)

•Unconstrained boundary conditions•Multiple spacecraft observations •Time scales ≤ few hours•Length scales ~100s RE

•Different plasma conditions than frequently studied (e.g. Magnetopause / magnetotail)

Advantages in studying Reconnection in the Solar Wind

Earth

ACE

Cluster

Wind

Exhaust

To Sun

Jet

Jet

BM

Solar Wind

Direction

Phan,T.D (2006)

131211109

5

0

-10

-5

20

0

-20

-40

-340

-350

-360

32m00s 34m00s02h 30m00s

|B| (

nT)

B (n

T)

Ion

Velo

city

(km

s-1)

Magnetic rotation at current sheets

Previous study of reconnection event 02/02/2002

Data from Cluster 3 in GSE

Total -- X --Y -- Z --

Phan,T.D (2006)

131211109

5

0

-10

-5

20

0

-20

-40

-340

-350

-360

32m00s 34m00s02h 30m00s

|B| (

nT)

B (n

T)

Ion

Velo

city

(km

s-1)

Magnetic rotation at current sheets

Previous study of reconnection event 02/02/2002

Data from Cluster 3 in GSE

Total -- X --Y -- Z --

Using Cluster’s 4 point-measurement capability it was not possible to reproduce these results.

Small scale features (e.g. Ripples in the current sheets) in these reconnection events?

•My study will initially look at the magnetic reconnection structures on a relatively small scale using the 4 Cluster spacecraft.

•This is in order to test more detailed reconnection models: is it possible to predict the outflow conditions given the inflow conditions?

•The extended study will look at the events on a larger scale using ACE and Wind.

Aim of Project

7

53h30m

6

6

40

20

0

52h30m 53h00m 54h00mUT

|B|

(nT)

Ion

Velo

city

En

hanc

emen

t (k

m s

-1)

Total -- X --Y -- Z --

Reconnection Exhaust

Magnetic Field and Ion Velocity Enhancement (GSE)

Cluster 3

54

2

-2

18

16

14

12

B (n

T)D

ensi

ty

(par

ticle

s cm

-3)

7

53h30m

6

6

40

20

0

52h30m 53h00m 54h00mUT

|B|

(nT)

Ion

Velo

city

En

hanc

emen

t (k

m s

-1)

Total -- X --Y -- Z --

Reconnection Exhaust

Magnetic Field and Ion Velocity Enhancement (GSE)

Cluster 3

54

2

-2

18

16

14

12

B (n

T)D

ensi

ty

(par

ticle

s cm

-3)

• Inflow 1 speed = 48kms-1

• Inflow 2 speed = 42kms-1

• Average exhaust speed = 45kms-

1

Minimum Variance Technique

•Results were consistent between spacecraft.

•In all cases:

•Normal direction vector taken as minimum variance direction

 

Current Sheet Orientation Determination

Sheet 1 Sheet 2

Earth

To the Sun

X-Line

Sheet 1Sheet 2

Solar Wind Direction

4min

int

Sheet 1 Sheet 2

Earth

To the Sun

X-Line

Sheet 1Sheet 2

Solar Wind Direction

X-line Direction•Cross product of the normal direction vector of each current sheet•Point on plane – position that Cluster 3 encounterssheet.•Right handed system for each current sheet

 

Assumption made: Current sheets can be

considered as flat planes

 

Current Sheet Co-ordinate System Determination

•Average velocity lies between current sheets•Perpendicular to X-direction

 

Exhaust Velocity Determination

Sheet 1

Reconnection Exhaust

Sheet 2

X-Point Cluster 3 trajectory through exhaust

• Comparing the data to more detailed reconnection models

• Looking at the small scale features in these large scale structures

• Comparing the Cluster data with data from ACE and Wind which also saw the event.

Ongoing Work

● Baumjohann, W. (1997): Wolfgang Baumjohann and Rudolf A. Treumann. Basics of Space Plasma Physics. Imperial College Press, 1997.

● Priest, E. R. (1984): Priest, E. R. (1984), Solar Magneto-Hydrodynamics, Geophys. Astrophys.Monogr. Ser., Springer, New York.

● Gosling, J.T (2005): J.T. Gosling, R.M. Skoug, D.J. McComas, C.W. Smith, J. Geophys. Res. 110, A01107, 2005

● Phan, T. D. (2006): T. D. Phan, J. T. Gosling, M. S. Davis, R. M. Skoug, M. Øieroset, R. P. Lin, R. P. Lepping, D. J.McComas, C. W. Smith, H. Reme, and A. Balogh. A magnetic reconnection X-line extending more than 390 Earth radii in the solar wind. Nature, 439:175–178, January 2006.

● Gosling (2007): J. T. Gosling, S. Eriksson,L. M. Blush,T. D. Phan,J. G. Luhmann,D. J. McComas,R. M. Skoug,M. H. Acuna,C. T. Russell, and K. D. Simunac. Five spacecraft observations of oppositely directed exhaust jets from a magnetic reconnection X-line extending > 4.26 106km in the solar wind at 1 AU

References

UCL DEPARTMENT OF SPACE & CLIMATE PHYSICSMULLARD SPACE SCIENCE LABORATORY

UCL DEPARTMENT OF SPACE & CLIMATE PHYSICSMULLARD SPACE SCIENCE LABORATORY

Minimum Variance Analysis

Cluster Configuration

B (n

T)

C1

C2

C3

C4

UT

Total -- X --Y -- Z --

Reconnection Event Interval

Magnetic Field (GSE)

Max R = 0.92 (x)Min R = 0.75 (y)

Max R = 0.99 (z)Min R = 0.76 (y)

Max R = 0.94 (z)Min R = 0.77 (y)

Max R = 0.99 (x)Min R = 0.36 (y)

Max R = 0.99 (z)Min R = 0.73 (y)

Max R = 0.99 (y)Min R = 0.58 (x)

4

0

-4

4

0

-4

4

0

-4

4

0

-4

52m00s 52m30s 53m00s 53m30s 54m00s 54m30s 55m00s

B (n

T)

C1

C2

C3

C4

UT

Total -- X --Y -- Z --

Reconnection Event Interval

Magnetic Field (GSE)

7654

7654

7654

7654

52m30s 53m00s 53m30s 54m00s 54m30s